Polyethylene terephthalate (also referred to as “PET”) is a polyester of terephthalic acid and ethylene glycol can be obtained by the polycondensation of dimethyl terephthalate with ethylene glycol, and also terephthalic acid with ethylene glycol or ethylene oxide. PET exists both as an amorphous (transparent) and as a semi-crystalline (opaque and white) thermoplastic material. Generally, it has useful chemical resistance to mineral oils, solvents and acids but not to bases. Semi-crystalline PET has good strength, ductility, stiffness and hardness. Amorphous PET has better ductility but less stiffness and hardness. PET is used to make bottles for soft drinks and other household and consumer products. Generally, PET has many uses and several large markets. For this reason, the volume of PET manufactured is large and growing.
Unfortunately, despite recycling efforts, billions of pounds of PET are still dumped into landfills annually all over the world. Other PET that is not reused is incinerated. The PET that is disposed into landfills creates significant waste. The incineration of PET wastes a significant resource that could be used more effectively.
Thermoplastic molding compositions based on polybutylene terephthalate (also referred to as “PBT”) and polyalkylene terephthalate are used in various applications. Although useful to many customers, conventional PBT-polyalkylene terephthalate molding compositions generally cannot be made from recycle sources of PBT due to the lack of availability of large post-consumer or post-industrial PBT. PET, unlike PBT, is made in much larger quantities and is more easily recovered from consumer wastes. If PET (scrap) materials could be converted to PBT and converted into useful molding compositions, then there would exist a valuable way to meet the unmet need to effectively use underutilized scrap PET in PBT thermoplastic molding compositions. If PET (scrap) materials could be converted to PBT and converted into useful molding compositions, then there would be an effective use of post consumer or post-industrial streams. PBT made this way would conserve our non-renewable resources and reduce the formation of greenhouse gases, e.g., CO2.
U.S. Pat. No. 5,451,611 teaches a process for converting waste polyethylene terephthalate to either poly(ethylene-co-butylene terephthalate) or poly butylene terephthalate (PBT) by reaction with 1,4-butanediol. In discussing the prior art, U.S. Pat. No. 5,451,611 indicates that in most of the processes it cites, the undesirable byproduct diethylene glycol is formed which contaminates the final product and has to be removed by purification before the recovered products can be reused again. A principal object of U.S. Pat. No. 5,451,611 was to provide a process for converting polyethylene terephthalate waste directly to another high value polymer without breaking down the polyethylene terephthalate to its constituent monomers or oligomers. The patent discloses numerous examples in which a variety of polymers have a diol incorporated at various amounts. Example 11 shows a PBT polymer being formed with a complete replacement of ethylene glycol with 1,4-butanediol.
U.S. Pat. No. 5,266,601 teaches a process for making “PBT” from PET by reacting PET with 1,4-butanediol. A principal object of U.S. Pat. No. 5,266,601 was to produce PBT containing less than 1.0 wt % units of ethylene glycol from PET scrap. Another principal objective of U.S. Pat. No. 5,266,601 was to develop a process that facilitates the reduction of THF generated in the process as much as possible to the extent that this PBT is economically competitive with PBT obtained from monomers. U.S. Pat. No. 5,266,601 emphasizes the production of PBT having ethylene glycol groups in an amount that is less than 1 wt %. In the instances where compositions contain more than 1 wt %, U.S. Pat. No. 5,266,601 presents these compositions in comparative examples. Such compositions are described as having “yellowish” and “slightly yellowish” colors, respectively.
Japanese laid-open application 2005-89572 teaches a method for producing polybutylene terephthalate by transesterifying bis(2-hydroxyethyl) terephthalate with 1,4-butanediol in the presence of a transesterification reaction catalyst under the pressure of 1-54 kPa at a final temperature ranging from 200-230° C. and then subjecting the reaction product to polycondensation. In one embodiment, the bis(2-hydroxyethyl) terephthalate is obtained by depolymerizing polyethylene terephthalate with excessive ethylene glycol, and purifying the depolymerized product. The patent teaches that transesterifying bis(2-hydroxyethyl) terephthalate with 1,4-butanediol under reduced pressure imparts favorable results.
Unfortunately, such documents do not meet the long felt need of improved use of PET scrap that is ordinarily incinerated or buried in landfills. U.S. Pat. No. 5,451,611, for instance, does not teach effective processes that enable PET to be able to be broken down into its constituent monomers or oligomers—a feature that is sometimes required by commercial considerations. U.S. Pat. No. 5,451,611 does not provide meaningful guidelines for making compositions functionally similar to PBT containing ethylene glycol in amounts other than trace amounts and which exhibit melting temperatures that are higher than those shown in its examples. Similarly, U.S. Pat. No. 5,266,601 does not provide meaningful details about how to make molding compositions containing combinations of polyalkylene terephthalates and PBT with a PET residue such as ethylene glycol in any amount, let alone an amount that is more than 1 wt %. In fact, neither patent discusses if or how the materials they describe can be used in molding compositions containing polyalkylene terephthalate and other materials such as flame retardants, epoxies, polycarbonates. Japanese laid-open application 2005-89572 is also silent about molding compositions containing fillers and PBT as well as methods for utilizing PET effectively to make such compositions. Known technology relating to utilizing PET as scrap materials for making PBT-like materials, in other words, does not provide meaningful solutions that solve the long felt need of new processes for better utilizing PET scrap that is ordinarily incinerated or buried in landfills. Known technology does not provide meaningful solutions that solve the long felt need of new thermoplastic compositions containing fillers, PBT derived from PET and a combination of physical properties that are highly useful and valued by customers.
For the foregoing reasons, there is a need to develop new molding compositions containing polyalkylene terephthalates that utilize PBT derived from PET and that have useful performance properties.
For the foregoing reasons, there is a need to develop new molding compositions that reduce the amount of CO2 emissions.
For the foregoing reasons, there is a need to develop new processes for making molding compositions that utilize PBT derived from PET and that have useful performance properties.